May make this condition worse. However the dose is usually not more than 40 mg 3 times a day. Use only the brand of this medicine that your doctor prescribed. Age greater than 50 years or Coronary artery disease or Crowded disc or low cup to disc ratio in the eye an eye disorder or Diabetes or Hyperlipidemia high fats in the blood or Hypertension high blood pressure or Non-arteritic anterior ischemic optic neuropathy or NAION serious eye condition , history of or Smoking—May increase the chance for a serious side effect in the eye called NAION. Using alcohol or tobacco with certain medicines may also cause interactions to occur. If your dose is different, do not change it unless your doctor tells you to do so. It continues to work for up to 4 hours, although its action is usually less after 2 hours.Cost Overdose Ask your doctor Q&A Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a .  · Sildenafil (Oral Route) Description and Brand Names Before Using Proper Use Precautions Side Effects Products and services Proper Use Drug information . RESOURCES GETTING STARTED WITH VIAGRA Your doctor has determined that VIAGRA may be right for you. Follow his or her instructions carefully to help you get the .